Distributed energy resources offer great potential for improving power quality and resiliency. Leading utilities who seek to take advantage of this potential are recognizing a major barrier: lack of standardization in DER operation and control. Addressing this, a major utility in the United States developed an operational standard for Battery Energy Storage Systems (BESS).
To implement the standard, they developed a test bed that allows them to comprehensively validate the operation of their DERMS controller before deploying new resources in the system. BESS behavior during various operational modes (including islanded), as well as effects on the operation of the system’s protection devices, can be evaluated.
The RTDS® Simulator provides a detailed model representing the behavior of the battery system, surrounding power system, and control loops. Simulation timesteps in the 50 microsecond range allow the representation of high frequency transients. The model runs in real time, allowing for fast and efficient simulation of many scenarios and the interfacing of external software or hardware to the simulated environment in a closed loop.
The operation of breakers and other control logic during islanding or reconnection can also be tested using real physical protective relays. In this case, the SEL 480E and 700G relays were interfaced to the simulation using analog and digital input and output. These relays are responsible for monitoring and operating the battery-side and main-side breakers.
Based on the characteristics and needs of their system, the utility defined many different modes which controllers must include in their functionality in order to comply with the new operational standard. Various real and reactive power functions, as well as islanding mode, are required. The set point, limits and permissions for these modes of operation are provided either locally in the simulation via user interaction, or remotely from the DERMS through DNP3.
Moving forward, with the implementation of the new operational standard, suppliers of BESS and their control systems will perform standardized tests on equipment prior to commissioning it on the utility’s network.